Alkoxy silyl capping agents for making terminally functionalized polymers

Abstract

The capping of anionic polymers to make functionalized polymers is improved by using alkoxy silyl compounds having protected functional groups, such as acetal groups, as the capping agent. The protected functional groups are stable under a variety of conditions and then readily convert to more reactive terminal functional groups useful for making adhesives, sealants and coatings.

We claim: 
     
       1. A process for making functionalized polymers, comprising the steps of: anionically polymerizing an unsaturated monomer with a mono-lithium or di-lithium initiator; and   terminating the polymerizing step by addition of an alkoxy silyl compound having the structure: ##STR5## wherein Y is an acetal group, a t-butyl dimethylsilyl group, or a trimethylsilyl ether group, and Z is a phenoxy radical or a trifluoroethoxy radical.   
     
     
       2. The process of claim 1, wherein the polymerizing step is initiated with a di-lithium initiator at a temperature from 20° C. to 60° C. 
     
     
       3. The process of claim 1, wherein the unsaturated monomer is selected from the groups consisting of styrene, 1,3-butadiene, and isoprene. 
     
     
       4. The process of claim 1, wherein Z is a phenoxy radical. 
     
     
       5. The process of claim 4, wherein the unsaturated monomer is 1,3-butadiene. 
     
     
       6. A process for making functionalized polymers, comprising the steps of: anionically polymerizing 1,3-butadiene with a monolithium or di-lithium initiator; and   terminating the polymerizing step by addition of an alkoxy silyl acetal compound having the structure: ##STR6## wherein Z' is a phenoxy radical or a trifluorethoxy radical.   
     
     
       7. The process of claim 6, wherein the polymerizing step is initiated with a di-lithium initiator at a temperature from 20° C. to 60° C. 
     
     
       8. The process of claim 7, further comprising the step of hydrogenating residual unsaturation in the functionalized polymer. 
     
     
       9. The process of claim 8, wherein Z' is a phenoxy radical.